Research On Detection Technology Of Internal Defects Of Security Lens

The lens is one of the core components of the security camera,which determines the efficiency and results of the entire surveillance.During the manufacturing process of the security lens,discrete local microscopic defects will be formed inside the lens due to improper operation,which will directly affect the imaging quality of the security lens.With the urgent demand for fine security and high precision,the requirements for the imaging quality of security lenses are becoming more and more stringent,and its qualified inspection standards can no longer meet the needs.Therefore,it is particularly important to detect microscopic defects inside the security lens.At present,security lenses rely on human eye observation for detection.Human eye observation and detection have many problems such as low efficiency,prone to visual fatigue,and limited by the technical level of workers.It is difficult to distinguish the types of defects and at the same time.The size of the disease is measured accurately and other issues.The market demand for security lenses is increasing,and there is an urgent need to develop new detection methods to solve this problem.The internal defects of the lens include bubbles,pits,scratches,and glue overflow,and new technologies need to be used for rapid and accurate detection.Based on the principle of scattering imaging,this paper uses a telecentric lens to collect bright background and dark defect images to obtain defect information,and proposes a new method of detecting internal defects of security lenses.The system consists of a telecentric lens,ring light and backlight lighting device,image acquisition and processing device.In a dark field environment,the backlight and ring light are used to illuminate the security lens to be tested,and then the object-side telecentric lens is used to image the high-resolution CMOS detector to obtain the defect image of the security lens to be tested.The front light and the back light are used in combination,and the object-side telecentric lens is manually adjusted to move along the Z axis to collect images inside the security lens.Then,the collected images are preprocessed with Halcon machine vision software.The pre-processed image information is processed by image superposition and image subtraction to obtain the internal defect information of the security lens to be detected.We use C#to compile the human-computer interaction interface to display the size,location and quantity of the defect in real time.And we use the RS485 communication protocol to control the PLC to control the lens to move according to the set step length,and call the Halconengine to start the image processing module,and the telecentric lens can collect a pattern at a time,and at the same time display the defect information in this state in real time,and it matches the corporate standard.Which determines whether the security lens is qualified,and finally realize the automatic detection of the internal defects of the security lens.The test results show that the resolution of the automatic detection system for detecting internal defects of the security lens is 100%,which can be applied to the automated production of industrial security lenses.